.TH tcpaccept 8  "2020-02-20" "USER COMMANDS"
.SH NAME
tcpaccept \- Trace TCP passive connections (accept()). Uses Linux eBPF/bcc.
.SH SYNOPSIS
.B tcpaccept [\-h] [\-T] [\-t] [\-p PID] [\-P PORTS] [\-\-cgroupmap MAPPATH] [\-\-mntnsmap MAPPATH]
.SH DESCRIPTION
This tool traces passive TCP connections (eg, via an accept() syscall;
connect() are active connections). This can be useful for general
troubleshooting to see what new connections the local server is accepting.

This uses dynamic tracing of the kernel inet_csk_accept() socket function (from
tcp_prot.accept), and will need to be modified to match kernel changes.

This tool only traces successful TCP accept()s. Connection attempts to closed
ports will not be shown (those can be traced via other functions).

Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bcc.
.SH OPTIONS
.TP
\-h
Print usage message.
.TP
\-T
Include a time column on output (HH:MM:SS).
.TP
\-t
Include a timestamp column.
.TP
\-p PID
Trace this process ID only (filtered in-kernel).
.TP
\-P PORTS
Comma-separated list of local ports to trace (filtered in-kernel).
.TP
\-\-cgroupmap MAPPATH
Trace cgroups in this BPF map only (filtered in-kernel).
.TP
\-\-mntnsmap  MAPPATH
Trace mount namespaces in this BPF map only (filtered in-kernel).
.SH EXAMPLES
.TP
Trace all passive TCP connections (accept()s):
#
.B tcpaccept
.TP
Trace all TCP accepts, and include timestamps:
#
.B tcpaccept \-t
.TP
Trace connections to local ports 80 and 81 only:
#
.B tcpaccept \-P 80,81
.TP
Trace PID 181 only:
#
.B tcpaccept \-p 181
.TP
Trace a set of cgroups only (see special_filtering.md from bcc sources for more details):
#
.B tcpaccept \-\-cgroupmap /sys/fs/bpf/test01
.SH FIELDS
.TP
TIME
Time of the event, in HH:MM:SS format.
.TP
TIME(s)
Time of the event, in seconds.
.TP
PID
Process ID
.TP
COMM
Process name
.TP
IP
IP address family (4 or 6)
.TP
RADDR
Remote IP address.
.TP
RPORT
Remote port
.TP
LADDR
Local IP address.
.TP
LPORT
Local port
.SH OVERHEAD
This traces the kernel inet_csk_accept function and prints output for each event.
The rate of this depends on your server application. If it is a web or proxy server
accepting many tens of thousands of connections per second, then the overhead
of this tool may be measurable (although, still a lot better than tracing
every packet). If it is less than a thousand a second, then the overhead is
expected to be negligible. Test and understand this overhead before use.
.SH SOURCE
This is from bcc.
.IP
https://github.com/iovisor/bcc
.PP
Also look in the bcc distribution for a companion _examples.txt file containing
example usage, output, and commentary for this tool.
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Brendan Gregg
.SH SEE ALSO
tcptracer(8), tcpconnect(8), funccount(8), tcpdump(8)
